What's good for the goose is not necessarily good for the gander – as the RSPB is discovering. With the UK having suffered its wettest April on record, some reserves have benefited from the rain, but others have been devastated.

Higher water levels at the Otmoor reserve in Oxfordshire have made reed beds wetter, giving birds such as bitterns a better chance of nesting. An increase in river flows has helped clear sediment, which is good news for fish generally, while on the Somerset Levels and moors, ground conditions are much better than if the dry weather had continued. "There's no reason now that birds like snipe, redshanks and lapwings there shouldn't have a successful summer," an RSPB spokesman said.

However, at several other of the wildlife charity's 211 nature reserves the floods have had a traumatic effect. The Ouse Washes reserve in East Anglia now lies under two metres of water, leaving the nests of an estimated 600 wading birds destroyed.

Almost two-fifths (37%) of England and Wales's lowland snipe, as well as redshank, lapwing and rare black-tailed godwits, have been affected by the adverse weather.

The RSPB's reserve managers had been attempting to manage water levels at a number of wetland nature sites in the face of drought. But conditions have now swung from one extreme to the other.

The Ouse Washes reserve, part of the flood relief system for the Great Ouse river, was hit by flooding after the Environment Agency was forced to open sluices on to the washes to prevent floods elsewhere on the 150-mile river catchment.

The RSPB said the agency was trying to find replacement land that could be managed for the birds to nest in, taking pressure off the Ouse Washes, an internationally important "special protected area" for birds.

Jon Reeves, site manager at the RSPB reserve, said: "Following centuries of land drainage across the UK, the Ouse Washes is now the most important stronghold for these birds after they have been largely forced out of other sites. Literally, we have all our eggs in one basket and we've lost them. It's devastating to watch the nests succumb to the rising waters without being able to do anything to prevent it."

Fairburn Ings reserve, in the Lower Aire valley near Castleford, west Yorkshire, was also flooded on Friday destroying hundreds of nests and burrows.

Chris Woolner, RSPB visitor experience manager at the site, said: "It has been a traumatic time because it is the beginning of spring and we have lost a lot of young wildlife which has just been washed away in the flood.

"The swan and duck feed platform in the main bay is completely covered and it has been impossible to manage this amount of water. We need people to come along to the centre to help out or donate money to help us."

There was at least one happy tale, after a coot family miraculously escaped from the floods. A nest full of eggs was washed away at Fairburn Ings but floated like a small life raft to a spot 30 metres away, where the eggs hatched.

Reeves said the RSPB's priority was finding replacement land for those birds whose habitat had been destroyed. "The Environment Agency is working hard to identify replacement land. Until this is in place, the birds will continue to face an uncertain future."

■ Two of the five cuckoos fitted with tracker devices to have their African migration mapped have returned to the UK. Lyster and Chris were fitted with the satellite tags last May by scientists from the British Trust for Ornithology (BTO). After a 10,000 mile trip, Lyster was seen 10 miles from where he was tagged.

Phil Atkinson, head of international research at the BTO, spotted the cuckoo on the Norfolk Broads on Tuesday. "We saw him flying past – you can see the wire antenna poking out [from his tag], so it was definitely him," he said.

Britain has lost almost half of its cuckoos in the last two decades and the population of the birds is continuing to decline steadily.